Date: Wed, 14 Mar 2001 16:57:27 -0600 From: Dan Nelson <dnelson@emsphone.com> To: Nate Williams <nate@yogotech.com> Cc: Dag-Erling Smorgrav <des@ofug.org>, freebsd-arch@FreeBSD.ORG Subject: Re: [PATCH] add a SITE MD5 command to ftpd Message-ID: <20010314165727.A2240@dan.emsphone.com> In-Reply-To: <15023.61042.768406.854325@nomad.yogotech.com>; from "Nate Williams" on Wed Mar 14 15:19:30 GMT 2001 References: <20010314105918.A5204@roaming.cacheboy.net> <35525.984597779@critter> <20010314210758.A2405@roaming.cacheboy.net> <15023.53743.215996.538067@nomad.yogotech.com> <20010314130025.A3031@dragon.nuxi.com> <xzpelw0yqun.fsf@flood.ping.uio.no> <20010314161646.A1482@dan.emsphone.com> <15023.61042.768406.854325@nomad.yogotech.com>
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In the last episode (Mar 14), Nate Williams said: > > Another thing to consider before adding SITE MD5 as a command is > > that it's an extremely slow operation. md5'ing a 10MB file takes > > about 1/3rd of a second on my pIII/600. It would take 5 minutes of > > CPU time to md5 1-gig worth of sources, and that's assuming that > > the FTP server is idle. ftpd would have to cache the md5 checksum > > somewhere for it to be acceptable, and then you've got the same > > caching problem (how does ftpd know when the file has changed to is > > can update its cached md5?). > > Is that cost greater than the cost of sending the data out over the > wire? Depends. Are we planning on only using the MD5 feature in Bill Fenner's port-checking scripts, or are we going to put it in bsd.port.mk? Do we want a thousand people doing "SITE MD5" commands every time a new copy of Netscape/Apache/kde/whatever comes out? You have to balance the cost of forcing an MD5 calc for every port fetch against the chance of a SIZE check returning a false-positive match. -- Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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